At 11:30 AM 8/20/2003, Mike Champion wrote:
>XQuery is probably a great breakthrough here by
>allowing both the implicit containment relationships
>that the relational model lacks and allowing documents
>to be composed by a Join operation on shared values,
>which AFAIK is the most profoundly powerful aspect of
>the RM.
There's a classic argument between hierarchy people and relational people
that goes back at least to the beginning of the relational model. The
hierarchical database people said that a direct representation of
relationships is really important. You don't drive your car up to the
garage, remove the wheels, put them in the wheels table, put the seats in
the seats table, etc. You just drive your car in and out.
The relational people said that relationships among data are so important
that they should be modeled as data so that they can be used as the basis
for queries and recombined in many ways. You may want to take the pieces of
many cars and put them together in some creative way. If all you want is
the original car, you don't need a real database.
XQuery says that both sides are right. It's important to be able to
maintain the original structure, and it's important to be able to do
queries based on that structure to create new structures.
Jonathan